> And be mindful that some frequency-standard devices contain > integrated DC-DC switching converters - like my HP 58540A GPS-DO.
> The noise from the HP DC converters was spraying RFI every 100 kHz > or so on the HF bands. After trying various RFI abatement > measures, including additional bypass C and toroid-wound #31 > ferrite material, my solution was scrap the entire PS board and > bring in clean power from a triple-output linear supply made by > Power-One. There's no switch-mode component anywhere in the path > of my GPS-DO. I'm having the opposite problem. The linear supply in my HP 53310A Modulation Domain Analyzer spews out a huge magnetic field that completely disupts any nearby equipment. For example, it causes a fuzzy trace and triggering problems on TEK 2467B scopes, which makes the scope unusable for low-level work. No amount of shielding has helped. I'm seriously considering making the 53310A DC power section into a switcher. I have developed some techniques that greatly reduce crosstalk by mounting circuits on their own grounded platform. These have a minimum number of connections to the main system ground, and are chosen to minimize switching currents from flowing on the main system ground. I put a brief description of the PST Prototype Platform on my web site at http://pstca.com/spice/pstpp/pstpp.htm Another technique that can help is adding an active filter to the output of the power supply. These can be very effective, but there are a number of approaches that are well-publicized that don't work very well. There is more analysis here: http://pstca.com/spice/ripple/ripple.htm Finally, Linear Technology supplies Low Noise Switching Regulators that can give ripple values of less than 100uV, which is comparable to or less than many linear regulators. If interested, see the links in the above url. Noise can be a tricky problem, but the above information might give some ideas to help tame it. Mike _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.